The present invention concerns a machine for cutting granite blocks or stone materials into slabs.
Some machines are known, exploiting different methods to cut granite into slabs.
A known type of machine uses a frame consisting of a variable number of vertically arranged steel blades which are parallel to one another and spaced from one another at a distance corresponding to the thickness of the slab to be obtained. Such blades are transversally connected with each other at their ends, so as to form a rigid structure.
The frame is driven so as to have a horizontal pendular working motion and a vertical descending sliding motion during which a paste consisting of iron or cast-iron grit mixed with water and lime is introduced at the contact point between the granite and the blade, so that it exerts its abrasive action.
This solution presents the inconvenience of causing considerable wear of the blades and of allowing very low feeding speeds in the range of 2 cm/h on a cutting width of approx. 3.5 m.
Another known method, which allows higher feeding speeds, performs the cutting action by means of a large steel disc with a diameter of up to 3.5 m on the periphery of which some diamond bits are attached.
The disc, which is driven by a powerful motor, performs a working motion by rotating around its axis and by a horizontal feeding motion in the direction of the length of the cut to be made. Although this cutting method allows good feeding speeds in the range of 20 cm/h, it presents some inconveniences.
A first inconvenience arises from the remarkably high costs of the disc and of the driving assembly. Another inconvenience is that the maximum height of the cut that can be made corresponds to the radius of the diamond disc minus the radial dimension of the flange for the attachment of the driving assembly.
Another cutting method uses a steel wire covered with an elastic diamond mixture.
The wire is made to slide on a vertical plane by means of a motor and two pulleys which rotate around horizontal axes and which are parallel to each other, one pulley being connected with the motor, while the other is idle and functions as a transmission.
Thus the working motion is transmitted to the diamond wire, while suitable means transmit to the pulleys a vertical downward motion, so as to impress to the diamond wire the feeding motion. The adjustment of the distance between the pulleys allows the adjustment of the width of the cut to be made.
This method also presents some inconveniences, such as the high stress exerted by the wire on the granite, since, during the working process, it slides on the entire cutting length. Moreover, the wire does not wear out evenly on the entire periphery, but only in the area which comes into contact with the granite to be cut. In any case, the main inconvenience is represented by the side skid of the diamond wire from the vertical plane during its downward feeding motion, which causes a poor superficial quality of the cut granite slabs.
Yet another machine is known, by means of which the abovementioned inconveniences are eliminated.
This machine consists of a portal-shaped structure on which there is a chain-guiding blade supporting a chain with diamond bits. The chain-guiding blade performs a downward vertical feeding motion, during which it also performs a series of pendular motions, while maintaining the co-planarity with the descending vertical plane. The chain with diamond bits, on the other hand, is driven so as to perform the working motion, consisting of a continuous rotation around the chain-support, which acts as a guide.
However, an inconvenience presented by this type of machine arises from the fact that the line of the cut is not straight.
The present invention has the purpose of eliminating all of the above-mentioned inconveniences.
The main proposed purpose is to obtain a machine wherein the cutting line is straight and horizontal during the entire working phase.
Another proposed purpose is to obtain a machine wherein the relative motion between the chain-guiding blade and the block to be cut is pendular.
Not the least proposed purpose is to obtain a machine according to the present invention costing remarkably less than the machines of the known types.
All the above-listed purposes and others, which will be better explained hereafter are reached by means of a machine for the cutting of granite or stone materials in general into slabs, which, in accordance with the present invention, includes a portal-shaped structure, at the top of which there is a chain, preferably with diamond bits, supported by a chain-guiding blade, around which it is stretched, following the same profile, the chain-guiding blade presenting at each end a threaded lead nut connected with a vertical threaded shaft, which is rigidly mounted on the post of the portal, the machine being characterized in that the chainguiding blade with its corresponding chain and the cut surface of the granite block which is being cut roll with a relative motion without skidding, since the space described by the centers of instantaneous rotation is a line coinciding with the profile of the cut.